Application of code division multiple access technology in readout circuit and system design for an ultra-thin on-cell flexible capacitive touch panel

Ying Jia Lin, Ying Cheng Su, Paul C.-P. Chao, Jia Yu Zhang, Eka Fitrah Pribadi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

A capacitive sensing circuit including electrodes for a 7-inch ultra-thin flexible on-cell touch panel has been designed. Implementing code-division multiple sensing (CDMS) with Walsh transform to scan Tx electrodes is chosen to improve the signal-to-noise ratio (SNR). The algorithm applies to field programmable logic array (FPGA). The sensing readout algorithm is applied to work on 4 Tx transmitter electrodes and 4 Rx sensing electrodes. The switched-capacitor (SC) circuit is applied to avoid disturbing sample signal from parasitic capacitance and enlarge the voltage difference from capacitance changes of the touch panel. 12-bit ADC to transfer the front-end analog signal to digital code. The digital part adopts a correction algorithm to eliminate the background value of the panel, the moving average algorithm has an adjustable signal-to-noise ratio function, and the Walsh conversion demodulation algorithm improves the touch report rate to achieve high SNR with up-to 34 dB.

Original languageEnglish
Title of host publicationASME 2019 28th Conference on Information Storage and Processing Systems, ISPS 2019
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791859124
DOIs
StatePublished - 27 Jun 2019
EventASME 2019 28th Conference on Information Storage and Processing Systems, ISPS 2019 - San Diego, United States
Duration: 27 Jun 201928 Jun 2019

Publication series

NameASME 2019 28th Conference on Information Storage and Processing Systems, ISPS 2019

Conference

ConferenceASME 2019 28th Conference on Information Storage and Processing Systems, ISPS 2019
CountryUnited States
CitySan Diego
Period27/06/1928/06/19

Keywords

  • CDMA
  • Finite element simulation
  • Multi-channel drive
  • On-cell capacitive touch panel
  • Readout circuit

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